CN112142032A - Porous charcoal containing three-dimensional amorphous carbon framework and preparation method and application thereof - Google Patents

Abstract

The invention provides a three-dimensional amorphous carbon frame porous charcoal and a preparation method and application thereof. The preparation method includes the following steps: pretreatment: making dry wood into wood blocks, and dissolving some components in the wood blocks through a solvent , enrich the micro-nano pore structure of the wood block to form a porous wood block; stabilize the pore structure: wash the porous wood block with deionized water several times, and then freeze-dry it; form amorphous carbon: pass the freeze-dried porous wood block through Double temperature gradient pyrolysis to obtain three-dimensional amorphous carbon framework-containing porous charcoal with nanoparticle decoration. The preparation method has simple preparation conditions; the prepared three-dimensional amorphous carbon frame porous charcoal has excellent comprehensive wave absorbing effect and can be used as a wave absorbing material, and the invention provides a new way for the value-added and efficient utilization of forest biomass.

Description

A kind of porous charcoal containing three-dimensional amorphous carbon framework and its preparation method and application

technical field

The invention belongs to the cross field of wave absorbing material technology and wood technology, and more particularly relates to a three-dimensional amorphous carbon frame porous charcoal and a preparation method thereof, and the application of the three-dimensional amorphous carbon frame porous charcoal as a wave absorbing material.

Background technique

While promoting the rapid development of society, electromagnetic technology inevitably brings serious threats to human physical and mental health, the operation of electronic equipment, and the stealth of weapons and equipment. Therefore, how to efficiently absorb polluting electromagnetic waves has received extensive attention and research in the civil and military fields. In addition to strong absorption capacity, excellent absorbing materials are also very important in light weight and wide effective absorption frequency band, which are also important development trends in the field of absorbing materials.

In recent years, new carbon materials (graphene, carbon nanotubes, etc.) have been widely used by researchers in the field of wave absorbing materials due to their good stability, low density, large specific surface area, and high electrical conductivity. However, single carbon materials such as graphene and carbon nanotubes are difficult to obtain ideal impedance matching conditions due to excessive electrical loss and no magnetic loss. The electromagnetic wave absorption ability is weak, and it is difficult to meet the requirements of high strength, broadband and light weight. In addition, the raw material (fossil) cost of these materials is high, and the preparation process is often complicated and energy consumption is high, which greatly restricts their further expansion and application. Forest biomass is a natural renewable resource, which not only has advantages in cost, environment, and carbon content, but also has highly ordered nutrient transport three-dimensional hollow microtubes that are difficult to achieve by conventional chemical synthesis, with regular pipelines and high porosity. The forest pyrolysis carbon based on three-dimensional ordered air micropipes, when electromagnetic waves are injected along the hollow pipes, most of the incident waves can be scattered and dielectrically attenuated in the micropipes, which can effectively reduce the radiation or interference of electromagnetic waves. In addition, nitrogen, phosphorus, iron, oxygen and other elements retained in the porous charcoal can optimize the dielectric loss and improve the impedance matching level, thereby enhancing the electromagnetic wave absorption capacity.

However, there are few studies on the application of forest biomass porous carbon materials in the field of absorbing materials, and the comprehensive absorbing effect is not ideal.

SUMMARY OF THE INVENTION

In view of the above-mentioned technical problems existing in the prior art, one of the objectives of the present invention is to provide a preparation method of porous charcoal containing three-dimensional amorphous carbon framework. The porous charcoal prepared by the preparation method can maintain the natural three-dimensional ordered pores of wood The introduction of nanopores and nanoparticles at the same time of structure makes the prepared porous charcoal have excellent comprehensive wave absorption effect under low filling degree.

In order to achieve the above object, technical scheme of the present invention is as follows:

A preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1, pretreatment: make dry wood into wood blocks, dissolve some components in the wood blocks through a solvent, enrich the micro-nano pore structure of the wood blocks, and form porous wood blocks;

S2. Stabilize the pore structure: the porous wood block is washed several times with deionized water, and then freeze-dried;

S3, forming amorphous carbon: the porous wood block treated in step S2 is pyrolyzed through a double temperature gradient to obtain a nanoparticle-modified porous charcoal containing a three-dimensional amorphous carbon framework.

The above-mentioned ways of making wood blocks from dry wood may include any methods disclosed in the prior art, including but not limited to sawing, cutting, and the like.

In some embodiments, the three-dimensional amorphous carbon frame-containing porous charcoal has a micro-nano hierarchical porous structure, the specific surface area is greater than 300 m2/g, and the density is less than 0.25 g/cm ³ .

In some embodiments, in the step S1, the solvent is an acidic sodium chlorite solution or a mixed solution of sodium hydroxide and sodium sulfite.

In some embodiments, in order to avoid the dissolution reaction destroying the natural three-dimensional ordered pore structure of the wood block (such as the cracking of hollow microtubules, collapse, etc.), the mass fraction of the acidic sodium chlorite solution is 1-10%, and the pH of the solution is 1-10%. The value is 2-4; preferably, the acid in this solution is one or more mixtures of hydrochloric acid, glacial acetic acid and sulfuric acid; the temperature of the reaction of the wood block in the acidic sodium chlorite solution is 20-100°C, the reaction time is 1-12h; preferably, the reaction temperature in the acidic sodium chlorite solution is 60-100°C, and the reaction time is 4-7h.

In some embodiments, in order to fully dissolve some components in the wood block and ensure that the hollow microtubes of the wood block are not damaged, the ratio of the mass of the wood block to the volume of the acidic sodium chlorite solution is (1- 3) g: 50 mL.

In some embodiments, the reaction temperature of the wood blocks in the mixed solution is 100-140° C., the reaction time is 1-12 h, and the mixed solution is a mixed solution of sodium hydroxide and sodium sulfite; preferably, the reaction The time is 3-7h.

In some embodiments, the ratio of the mass of the wood block to the volume of the mixed solution is (1-5) g:50 mL.

In some embodiments, in the step S3, the first temperature of the pyrolysis is 180-300° C., and the temperature is kept for 2-5 hours, which can be carried out by using an oven, a tube furnace, a muffle furnace, etc., and the gradient temperature can be used to carry out treatment, which can further stabilize the three-dimensional micro-nano porous framework and promote the formation of nanoparticles; the second temperature is 500-750 ° C, and the temperature is kept for 1-3 h, which can be carried out in a tube furnace or muffle furnace filled with an inert protective atmosphere, and the gradient is used. The temperature can convert the carbon-containing components in the wood into amorphous amorphous carbon with weak conductivity.

In some embodiments, in the step S2, freeze-drying can ensure that the three-dimensional ordered hollow microtubes and nanopore structures in the wood block do not undergo changes such as collapse, shrinkage, etc. during the drying process, and the preferred drying temperature is ( -40)-(-80) ℃, drying time is 48-60h.

Another object of the present invention is to provide a three-dimensional amorphous carbon frame-containing porous charcoal prepared by the method for preparing a three-dimensional amorphous carbon frame-containing porous charcoal according to any one of the above embodiments.

The third object of the present invention is to provide a wave absorbing material prepared from the above-mentioned porous charcoal containing a three-dimensional amorphous carbon frame.

Compared with the prior art, the beneficial effects of the present invention are as follows:

The present invention utilizes the three-dimensional ordered hollow microtubule structure of wood and at the same time utilizes the partial dissolution of the components in the wood to make the wood block have a micro-nano hierarchical porous structure, so as to obtain a porous wood block with a large specific surface area; Remove the chemicals in the wood and use freeze-drying to ensure that the micro-nano pore structure does not collapse and shrink during the drying process, and stabilize the three-dimensional pore structure; finally, the freeze-dried porous wood block is pyrolyzed through a double temperature gradient. , first pyrolyzed at the first temperature to further stabilize the three-dimensional micro-nanopore structure and promote the formation of nanoparticles, and then pyrolyzed at the second temperature to change the carbon-containing components in the wood into amorphous amorphous with weak conductivity carbon.

The preparation method provided by the invention has the advantages of simple preparation process and low cost, and is favorable for industrial production.

The three-dimensional amorphous carbon frame-containing porous charcoal prepared by the preparation method provided by the present invention has the characteristics of large specific surface area, moderate conductivity and good impedance matching. Moreover, it has the advantages of high absorption strength under low filling degree, effective absorption frequency bandwidth, etc., and its absorbing performance is excellent. It has great application prospects in the field of absorbing materials, and can be used as absorbing materials. The invention provides a new way for the value-added and efficient utilization of forest biomass.

Description of drawings

Fig. 1 is the flow chart of the preparation method of the present invention;

Fig. 2 is the XRD spectrum of the porous charcoal containing three-dimensional amorphous carbon framework prepared in Example 1 of the present invention;

3 is an SEM image of the porous charcoal containing three-dimensional amorphous carbon framework prepared in Example 1 of the present invention;

4 is a reflection loss diagram of the porous charcoal containing a three-dimensional amorphous carbon framework prepared in Example 1 of the present invention.

Detailed ways

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementation disclosed below.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

Example 1

As shown in Figure 1, a preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1. Pretreatment: Saw the native wood (take masson pine as an example, air-dried or absolutely dry) into 10mm thick wood blocks, put the wood blocks into 500mL of acid sodium chlorite solution with a mass fraction of 2%, Treated at a temperature of 60-75°C for 6-7 hours, some components in the wood block are dissolved out, the micro-nano pore structure of the wood block is enriched, and a porous wood block is formed; wherein, the pH of the solution is 2, and the ratio of wood block mass to solution volume is 3g: 50mL;

S2. Stabilize the pore structure: Wash the porous wood block with deionized water several times to remove the residual chemicals; then freeze-dry it at -50°C for 50h;

S3. Formation of amorphous carbon: Put the porous wood block after drying in step S2 into a tube furnace filled with inert gas, first heat up to 250°C and keep it for 2h, then heat it up to 650°C and keep it for 3h, then cool to 250°C. At room temperature, nanoparticle-modified porous charcoal containing a three-dimensional amorphous carbon framework was obtained.

The porous charcoal containing the three-dimensional amorphous carbon framework prepared in this example was characterized by XRD and SEM, respectively. The XRD analysis diagram is shown in FIG. 2 , and the SEM analysis diagram is shown in FIG. 3 .

As shown in Figure 3, the porous charcoal containing a three-dimensional amorphous carbon framework prepared in this example has a high specific surface area. After testing, the specific surface area is greater than 300 m2/g, and the density is less than 0.25 g/cm ³ ; the average pore size of the three-dimensional amorphous carbon framework is about 20 μm, and the nanoparticle filling in the three-dimensional amorphous carbon framework is low.

The three-dimensional amorphous carbon frame porous charcoal prepared in this example was pressed into concentric rings with an outer diameter of 7 mm and an inner diameter of 3.04 mm, and the electromagnetic performance was tested. The reflection loss performance at different thicknesses is shown in Figure 4.

As shown in Figure 4, the reflection loss of the porous charcoal containing three-dimensional amorphous carbon frame prepared in this example is all below -30dB. When the thickness is 2.5mm, the wave absorption performance is remarkable, and the optimal reflection loss reaches -64dB.

Example 2

A preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1. Pretreatment: Saw the native wood (air-dried or absolutely dry) into wood blocks with a thickness of 7mm, put the wood blocks in 500mL of an acidic sodium chlorite solution with a mass fraction of 5%, at 80-90 ℃ After treatment for 5-7 hours, some components in the wood blocks are dissolved out, and the micro-nano pore structure of the wood blocks is enriched to form porous wood blocks; wherein, the pH value of the solution is 4, and the ratio of the mass of the wood blocks to the volume of the solution is 1 g: 50 mL;

S2. Stabilize the pore structure: wash the porous wood block with deionized water several times to remove the residual chemicals in the porous wood block; then freeze-dry it at -80°C for 48 hours;

S3. Formation of amorphous carbon: put the porous wood block after drying in step S2 into an oven, first heat it up to 200°C and keep it for 5 hours, then take out the sample after cooling; then put the sample into a tube filled with an inert protective atmosphere The temperature was raised to 750 °C in the furnace and kept for 1 h. After cooling, the porous charcoal containing three-dimensional amorphous carbon framework decorated with nanoparticles was obtained.

Example 3

A preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1. Pretreatment: Saw the native wood (air-dried or absolutely dry) into wood blocks with a thickness of 5mm, put the wood blocks in 500mL of an acidic sodium chlorite solution with a mass fraction of 3%, and treat them at 100 ° C for 5 -7h, some components in the wood block are dissolved out, the micro-nano pore structure of the wood block is enriched, and a porous wood block is formed; wherein, the pH value of the solution is 3, and the ratio of the mass of the wood block to the volume of the solution is 2g:50mL;

S2. Stabilize the pore structure: Wash the porous wood block with deionized water several times to remove the residual chemicals in the porous wood block; then freeze-dry it at -50°C for 48h;

S3. Formation of amorphous carbon: put the porous wood block after drying in step S2 into an oven, first heat it up to 250° C. and keep it for 3 hours, and then take out the sample after cooling; The temperature was raised to 700 °C in the furnace and kept for 2 h. After cooling, the porous charcoal containing three-dimensional amorphous carbon framework modified by nanoparticles was obtained.

Example 4

A preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1. Pretreatment: Saw the native wood (air-dried or absolutely dry) into wood blocks with a thickness of 10 mm, put the wood blocks into 500 mL of a mixed solution composed of sodium hydroxide and sodium sulfite, and treat them at 120 ° C for 5 hours. Part of the components in the wood block enriches the micro-nano porous structure of the wood block to form a porous wood block; wherein, the ratio of the mass of the wood block to the volume of the mixed solution is 3g:50mL;

S2. Stabilize the pore structure: Use deionized water to repeatedly wash the porous wood block to remove the residual chemicals in the porous wood block; then freeze-dry at -50°C for 48h;

S3. Formation of amorphous carbon: Put the porous wood block after drying in step S2 into a tube furnace filled with an inert protective atmosphere, first heat it up to 200°C and keep it for 5 hours, then heat it up to 600°C and keep it for 2 hours to obtain nanoparticles Modified porous charcoal with three-dimensional amorphous carbon framework.

Example 5

A preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1. Pretreatment: Saw the native wood (air-dried or absolutely dry) into wood blocks with a thickness of 7 mm, put the wood blocks into a mixed solution of 500 mL of sodium hydroxide and sodium sulfite, and treat them at 100 °C for 7 hours to dissolve the wood blocks. The middle part of the component enriches the micro-nano pore structure of the wood block to form a porous wood block; wherein, the ratio of the mass of the wood block to the volume of the mixed solution is 5g:50mL;

S2. Stabilize the pore structure: Wash the porous wood block with deionized water several times to remove the residual chemicals in the porous wood block; then freeze-dry it at -50°C for 48h;

S3. Formation of amorphous carbon: Put the porous wood block after drying in step S2 into a muffle furnace filled with an inert protective atmosphere, first heat it up to 250 °C and keep it for 3 hours, then heat it up to 650 °C and keep it for 2.5 hours, then cool it down Then, nanoparticle-modified porous charcoal containing three-dimensional amorphous carbon framework was obtained.

Example 6

A preparation method of porous charcoal containing three-dimensional amorphous carbon framework, comprising the following steps:

S1. Pretreatment: Saw the native wood (air-dried or absolutely dry) into wood blocks with a thickness of 15 mm, put the wood blocks into a mixed solution of 500 mL of sodium hydroxide and sodium sulfite, and treat them at 140 ° C for 5 hours to dissolve the wood blocks. The middle part of the component enriches the micro-nano porous structure of the wood block to form a porous wood block; wherein, the ratio of the mass of the wood block to the volume of the mixed solution is 3g:50mL;

S2. Stabilize the pore structure: Wash the porous wood block with deionized water several times to remove the residual chemicals in the porous wood block; then freeze-dry it at -80°C for 60h;

S3. Formation of amorphous carbon: Put the porous wood block after drying in step S2 into a muffle furnace filled with an inert protective atmosphere, first heat it up to 300 °C and keep it for 2 hours, then heat it up to 750 °C and keep it for 1 hour, after cooling Nanoparticle-modified porous charcoal containing three-dimensional amorphous carbon framework was obtained.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. A preparation method of porous charcoal containing a three-dimensional amorphous carbon framework comprises the following steps:

s1, preprocessing: preparing dry wood into a wood block, dissolving out part of components in the wood block through a solvent, and enriching a micro-nano pore structure of the wood block to form a porous wood block;

s2, stable pore structure: washing the porous wood block for several times by using deionized water, and then freeze-drying;

s3, amorphous carbon: and (4) pyrolyzing the porous wood block treated in the step S2 through double temperature gradients to obtain the nanoparticle-modified porous charcoal containing the three-dimensional amorphous carbon framework.

2. The method for preparing porous charcoal containing a three-dimensional amorphous carbon frame according to claim 1, wherein the porous charcoal containing a three-dimensional amorphous carbon frame has a micron-nanometer hierarchical porous structure, a specific surface area of more than 300 square meters per gram and a density of less than 0.25g/cm³。

3. The method for preparing porous charcoal containing three-dimensional amorphous carbon framework according to claim 1, wherein the solvent is an acidic sodium chlorite solution or a mixed solution of sodium hydroxide and sodium sulfite in step S1.

4. The method for preparing porous charcoal containing three-dimensional amorphous carbon framework according to claim 3, wherein the acidic sodium chlorite solution has a mass fraction of 1-10% and a pH value of 2-4; the reaction temperature of the wood blocks in the acidic sodium chlorite solution is 20-100 ℃, and the reaction time is 1-12 h.

5. The method for preparing porous charcoal containing three-dimensional amorphous carbon framework according to claim 4, wherein the ratio of the mass of the wood block to the volume of the acidic sodium chlorite solution is (1-3) g:50 mL.

6. The method for preparing porous charcoal containing a three-dimensional amorphous carbon frame as claimed in claim 3, wherein the reaction temperature of the wood block in the mixed solution is 100-140 ℃ and the reaction time is 3-7 h.

7. The method for preparing porous charcoal containing three-dimensional amorphous carbon framework according to claim 6, wherein the ratio of the mass of the wood piece to the volume of the mixed solution is (1-5) g:50 mL.

8. The method as claimed in claim 1, wherein the pyrolysis step S3 comprises the steps of pyrolysis at a first temperature of 180 ℃ and 300 ℃ for 2-5 h; the second temperature is 500-750 ℃, and the temperature is kept for 1-3 h.

9. A porous charcoal containing a three-dimensional amorphous carbon framework, which is prepared by the method for preparing a porous charcoal containing a three-dimensional amorphous carbon framework according to any one of claims 1 to 8.

10. A wave-absorbing material prepared from the porous charcoal containing the three-dimensional amorphous carbon framework of claim 9.

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